Advances in fiber laser technology have resulted in the increased use and availability of several high-power laser systems operating in the mid-infrared band with short switching times and high modulation rates. The current American National Standard for the Safe Use of Lasers (ANSI Z136.1-2014) defines the calculation of the maximum permissible exposure (MPE) on the skin in terms of the exposure duration a single pulse or the total exposure time limit, and is based on continuous-wave laser skin exposure minimum visible lesion (MVL) data. This study determined the MVL data thresholds in Yucatan miniature pig skin for multiple-pulse 1940-nm laser exposures with pulse repetition frequencies (PRFs) of 100, 200, and 1000 Hz, and trains of 300, 1000, or 3000 pulses. The individual pulse duration in each exposure train was 500 µs. We report the MVL thresholds as the median effective dose (ED50) based on varying individual pulse energy. The results highlight the effect of PRF on the thresholds for multiple-pulse cases. Comparison with the existing ANSI Z136.1 MPE limits provides a calculation of the safety margin for each parameter case.
Neodymium-doped yttrium aluminum garnet (Nd:YAG) lasers are among the most commonly used lasers with a wide variety of applications from biomedicine to manufacturing. The ubiquity of these lasers increases the likelihood of accidental ocular injury resulting in permanent visual impairment. We performed dosimetry studies to determine retinal damage thresholds and hemorrhagic lesions in the porcine eye with Qswitched Nd:YAG lasers. The Yucatan miniature pig model exhibited similarities in ocular anatomy to human eyes. The Nd:YAG laser, tuned to 1064 nm with a pulse width of seven nanoseconds, delivered laser energy to the retina. Retinal imaging modalities including fundus photography, real-time video, confocal scanning laser ophthalmoscopy (cSLO), and spectral domain optical coherence tomography (SD-OCT) provided visualization of retinal morphology at multiple time points. Retinal damage thresholds were grouped into three categories: minimum visible lesion (MVL), contained hemorrhagic lesion (CHL), and vitreal hemorrhagic lesion (VHL). Probit analysis determined the effective dose for 50% probability of damage (ED50) for each lesion category. The threshold to produce a MVL was 0.193 mJ based on 24-hour assessments of the retina. The one-hour hemorrhagic lesion thresholds were 0.408 mJ and 1.52 mJ for CHL and VHL, respectively
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